Conventionally, when remaining capacity of a battery is equal to or less than a low limit threshold, so that the remaining capacity of the battery becomes a target value, as a vehicle control system, for example, a hybrid vehicle control system disclosed in patent literature 1 is known. In the vehicle control system, a control device controls a power conversion device to convert generation power of an engine and a motor generator.
The hybrid vehicle control system includes an engine, a power storage device, a motor generator, a power converter, and an ECU. The power storage device, the power converter, and the ECU correspond to a battery, a power conversion device, and a control device, respectively.
As described in patent literature 1, when a SOC of the power storage device goes down to a low limit threshold SL, the ECU causes the engine to drive and the motor generator to generate electric power. The SOC represents remaining capacity of a battery and represents a ratio of the remaining capacity to capacity at the time of full charge. The ECU controls the power converter to convert electric power generated by the motor generator and charges the power storage device.
When the SOC of the power storage device reaches an upper limit threshold SU, the ECU stops the engine and terminates the charge of the power storage device.
The inventor of the present application has found the following. The power storage device has a characteristic that a maximum input power reduces when temperature decreases. In a case where the upper limit threshold SU, which is the target value of the SOC, is consistent irrespective of the temperature of the power storage device, when temperature of the power storage device decreases, the electric power that can be supplied to the power storage device, that is, allowable input power, may reduce. A driving condition of the engine may be restrained when the allowable input power reduces and electric power, which is supplied to the power storage device, is generated by the motor generator. For example, the engine may not drive on an efficient drive condition. Fuel consumption of a vehicle may get worse.
Patent literature 1: JP 2013-001373 A